This disclosure relates to thin film photovoltaic solar cells.
In a copper/gallium/selenium (“CIGS”) thin film solar cells, the thin film stack generally comprises a substrate, a molybdenum (“Mo”) thin film layer as a back contact layer (a.k.a., back electrode), and a CIGS thin film layer as the absorber layer. The structure can further include a buffer layer of CdS, for example. A top electrode layer (a.k.a., front contact or transparent conductive oxide layer) is provided above the buffer layer. Such structure is formed by first depositing the molybdenum thin film layer over the substrate. The CIGS thin film absorbed layer is formed by deposition of a Cu/In/Ga (CIG) intermetallic precursor layer on the Mo thin film layer and followed by selenization and optionally sulfurization of the CIG precursor in a furnace, thus, converting the CIG precursor layer into the final CIGS layer.